There are federal laws barring agents from tampering with amateurs and most states have laws, but jail time isn't a concern for these people. Risk vs reward. You give Fletcher Cox, a kid from a rough neighborhood in a poor town who's momma lives in a trailer while you're projected to be a team's #1 pick, (throwing a number out there) $25,000 as an advance so that he'll sign a long term contract and the WORST thing that could happen is the state of Mississippi fines you... I don't know... $20,000? So your total investment on a guy who's a #1 pick is $45,000 and you'll likely recoup that PLUS some on his first 3-4 year rookie contract.
That's IF the state of Mississippi will go and get you. Most states don't give a **** because it would cost them a **** load of money to pay a team to investigate an agent and even more money to take the agent to court... and 90% of agents are lawyers while 100% of agencies have lawyers on their payroll that are better than the state counterparts.
It's a total joke.