A good prosecutor can indict a ham sandwich.
The original phrase, attributed to New York judge Sol Wachtler, from 1985, went something like this:
“[If a district attorney wanted, a grand jury would] indict a ham sandwich.”
It was immortalized in the Tom Wolfe novel "Bonfire of the Vanities" (1987).
The phrase succinctly summarizes the state of legal affairs where a prosecutor can find some law written somewhere that even the most well-behaved citizen has broken.
Update
For those who think that being indicted is less severe than being convicted, you may want to become familiar with the process and its consequences, as described in Ham Sandwich Nation: Due Process When Everything Is a Crime (Glen Reynolds, Columbian Law Review, July 8, 2013) on how prosecutors might pick the laws they choose to indict under in order to obtain likely conviction. In the end, this can make indictment vs. conviction a distinction without a difference. This is exactly what the OP is describing.
Taking the quote from the article:
It would then be up to the junior prosecutors to figure out a plausible crime for which to indict him or her. The crimes were not usually rape, murder, or other crimes you’d see on Law & Order but rather the incredibly broad yet obscure crimes that populate the U.S. Code like a kind of jurisprudential minefield: Crimes like “false statements” (a felony, up to five years), “obstructing the mails” (five years), or “false pretenses on the high seas” (also five years). The trick and the skill lay in finding the more obscure offenses that fit the character of the celebrity and carried the toughest sentences. The, result, however, was inevitable: “prison time.”
So, if the prosecutor wanted to convict someone, then some obscure crime with a severe penalty would be found that would apply.
You could consider using "political gimmick". "Gimmick" means:
A trick or device intended to attract attention, publicity, or trade:
'it is not so much a programme to improve services as a gimmick to gain
votes'
[Oxford Online Dictionary]
What evidence is there that Lyndon Johnson's War on Poverty was more
than a "political gimmick"?
Best Answer
How about "to cash in on"?
E.g. But Adam and Eve, (the first husband and wife), our original human parents did not control their lustful cravings, and the serpent cashed in on their weakness...
"Play on (or upon)" could also do the trick, as well as the more formal -- yet idiomatic -- "avail oneself of" and "turn...to (good) account".
He played on his enemies' weaknesses, surprised them when they thought they couldn't be misled. source
Clever enough to discern the causes necessitating the cessation of treaty or war with an enemy, or to lie in wait keeping treaties, obligations and pledges, or to avail himself of his enemies' weak points, making jokes with no loss of dignity or secrecy... source
They availed themselves of the weaknesses, the selfishness and the self-interest of man... source
The politician of today knows men, and he knows how to turn their weaknesses to account. source