Rules are well and good, but norms are important too. An immigration system governs people making major life choices, and companies making large investments.

Legally, there's very little the state can't do, there could be a bill passed tomorrow revoking all immigrant visas. But businesses, and by proxy the nation, benefit from work done by these workers.

Sudden unilateral moves like this are stupid on a social level (cause damage to businesses and communities), and on a moral level. "First do no harm" is a principle just as suited to government as medicine. Even if there is a broad consensus for reducing or eliminating H1B visas, why punish people who followed the system as it exists and contributed? It's perfectly possible to pass a bill, stop handing out new visas, and sunset renewals after some 1-2 year timeframe.

It's legal to invite a bunch of guests over and kick them all out after you open the wine, but you're going to lose friends. And ultimately it will be businesses and individuals paying the cost for these needlessly volatile course changes. Tourism and high skilled immigration rates will face lasting harm.