As a health inspector for over 20 years, I am astounded by the lack of awareness that food safety controls are based on science and not on individual inspectors' personal fears and bad moods. Botulism control is based on some of the following facts: botulinum spores are commonly found in soil and on vegetable surfaces, botulinum grows in low or no oxygen envt., botulism has high virulence. (Virulence is a technical term for the fact that a high number of botulism victims end up dead (like Listeriosus of raw milk fame), in contrast to other food borne illnesses like Staph or Campyllobacter.) When considering the fact that botulinum grows slowly, and food borne illnesses whack people more often with weak immune systems, such as the elderly, the ill, and the very young, the food producer may have just been lucky that the product never created a problem, or the very real option that a problem was never narrowed down to the product.
As to the argument that old time recipes have been made for centuries, as in this case, (I am a bit of a foodie and Italian), the big difference is that many products were never made for mass production and or to stick around on shelves for long periods of time, and if so, any data, let alone food safety data, is unavailable for historic food products. In fact, the link between bacteria and illness was scientifically proven by Koch as late as the late 1800's. Another fact is that the CDC's data shows that outbreaks over the last 50 years are fewer, involve much higher number of victims and are more often associated with mass production and distribution of food. My health dept. receives notices of food recalls at least once a week.
In the case of botulism and fresh garlic in oil, it's considered so risky that acidification is required nationwide. In California, there is a state lab that specializes in evaluating botulism safety for commercial operations. (It's funded by taxes to keep cost to businesses low and is considered a public service.) I would recommend that producers contact their State health depts. and work with them to identify any and all options available for the canning and sale of any low acid food - including acidification, using dried ingredients, temperature control, flash heating (called a "kill step"). The majority of us inspectors truly focus on how to sell food safely and do not approach their jobs as stopping people from making a living. And surprise surprise we don't always think alike, just don't get me started. However, I'll finish with the following consideration of the implication that "life has it's many risks" argument that we inspectors hear often. When it comes to death, the public, the politicians and the members of responsible industry itself does not tolerate "a little death."
We had a very similar question about making your own garlic oil here:
Botulism, Garlic, Cold pressed Olive oil and mason jars
Oil is effectively an anaerobic environment, which promotes the growth of the bacteria and spores responsible for botulism.
However, these types of risks are common in home canning. Major factories producing canned or bottled goods are going to want to protect themselves against millions of lawsuits, so they are going to take steps to pasteurize (for lack of a better word) the foods before packaging them. Commercially-packaged infused oils have probably either been heated, acidified, or filtered to guarantee food safety.
On the other hand, the linked question above demonstrates that there are people out there who aren't taking the appropriate precautionary measures. If this oil came from a well-known company with a good track record then I would not worry (and you can always contact them if you are worried); however, if it came from somebody you've never heard of, and can't find any reliable information on - i.e. somebody who's making this stuff from home - then I might be a little more concerned.
If you trust the source, then trust the oil. Otherwise, you might want to try sterilizing it yourself; you need to either heat it to 250° F (121° C) or expose it to acid conditions. Neither of those things are really desirable; heating it can taint the flavour or even burn the oil depending on what kind of oil it is, and if you want to take the acid route, you basically need to to pickle it. But there you have it, that's what you can do if you don't trust the safety.
Best Answer
According to research conducted at the University of Idaho and published in 2014 in the journal Food Protection Trends, there are now consumer guidelines to process garlic (and certain herbs) safely through acidification before adding to oil.
I would read the first link thoroughly to understand the necessary process. To ensure safety, follow the steps precisely. (The second link provides the original scientific paper with detailed data and testing protocols.)
To summarize the procedure:
Peel and chop garlic so that pieces are no more than 1/4" long in any dimension. (Whole cloves or larger pieces are NOT acceptable, since the acid needs to penetrate fully.)
Make a 3% solution of citric acid by combining 1 level Tablespoon of granular citric acid with 2 cups of water. (Note that other acids, lemon juice, vinegars, etc. have NOT been verified and tested for safe home use in this step.)
Combine chopped garlic with a 3% solution of citric acid in a ratio of 1 part garlic to 3 parts citric acid by weight. This is about 2/3 cup of chopped garlic, if you use the amount of acid in step (2).
Let garlic soak in the acid for 24 hours. (This is a minimum to ensure safety; a longer soak may be used, but it could degrade the flavor.)
Drain the acidified garlic well. Combine the acidified garlic with oil, and infuse. A ratio of 1 part garlic to 10 parts oil by weight is recommended, but the ratio can be varied from this to achieve appropriate flavor.
While the procedure recommends removing the garlic once appropriate flavor has been achieved (generally in 1 to 10 days), there is no food safety risk if the garlic is kept in the oil for longer.
As for storage, they write: "Refrigeration of these infused oils is recommended for quality, but not required for safety." And later:
The scientific paper also notes that the taste and quality of the infused oil produced using this home method was not less than infused commercial oil:
Note that acidification is the essential step here and is the only method tested for home use so far to ensure safety for longer storage. The paper specifically notes that there are no approved procedures for pressure canning garlic in oil at home, and non-acidified garlic in oil mixtures must be refrigerated (and used within 2 to 4 days) or frozen.
IMPORTANT DISCLAIMER: Food preservation is not to be taken lightly, particularly in situations that are known risks for botulism. People who are familiar with home canning recipes already know that one should only use approved recipes and procedures that have been thoroughly tested; this procedure is no exception. Botulism risks are generally low, but the consequences of deviating can be severe.
If you are not willing to go through this detailed procedure (or another one approved by a reputable food safety and preservation organization), be sure to store any garlic-infused oils in the refrigerator and use within 2-4 days or freeze.