If a law is unenforceable, what's the point of having it on the books? This seems like just another way for the state to extract revenue from the public, and furthermore if it is enforced, it will be enforced unevenly. In the United States, such a proposal would impact those that are already the disproportionate victims of police harassment, black and brown working class people, moreso than it would actually 'protect' women walking down the street from catcalling.
If you're actually interested in preventing this kind of behavior (which stems from the subordinate position of women in class society), you'd be better off addressing the structural issues that create male chauvinism, not just throwing a band-aid on it and calling everything well and good. This might sate your guilty liberal conscience, but it won't ultimately address the root cause of the problem, and in the end, it will probably make things worse.
Horrible Proposal.
I always find it interesting on how we come to the same conclusion on issues like these despite our differing beliefs and thought patterns. I consider this HP too.