[bpodgursky]

That's just not true, many jurisdictions don't allow electronic devices, for exactly this reason: https://www.bustle.com/p/can-i-use-my-phone-while-voting-all...

[thatswrong0]

I'm sure it's illegal to pressure someone to vote a certain way as well. Do you really think someone is monitoring someone's voting booth to see if they're using their phone? Wouldn't that be in exact violation of the problem you're talking about?

How would this be enforced?

Very silly.