President Biden is pleading with Congress for new authority to shut down the nation’s overwhelmed southern border, declaring that he has done “all I can do” and urging lawmakers to “give me the power” to fix it.

“We don’t have enough agents. We don’t have enough folks. We don’t have enough judges,” Mr. Biden said on Monday. “Why won’t they give me the help?”

A Senate bill introduced over the weekend tries to do just that. But it is fiercely opposed by House Republicans, who insist the president has simply failed to wield the power over immigration that he already has.

Who’s right?

While it is true that there are some steps Mr. Biden could take without Congress, the idea that he has unfettered power to seal the country off is far too simplistic. The United States also has laws that require the government to consider asylum claims from people fleeing persecution. Any attempts to circumvent that would almost certainly face legal challenges.

The proposed legislation would clear away legal, practical and financial roadblocks to stiffer enforcement at the border that both parties say they want.

Veterans of decades of political and policy debates over immigration said the bill would give Mr. Biden explicit new authority to deny asylum claims, expel people from the country more quickly and keep track of migrants while they are in the United States.