Republican-led Washington is mulling the most far-reaching changes to federal labor policy in seven decades in ways that could strengthen businesses and individual workers while weakening unions’ labor power as well as political strength.

The effort goes beyond rewriting parts of workplace law. The Supreme Court, the White House, leaders in Congress, and even state legislatures are all fundamentally rethinking its underlying principles: who it is meant to protect, and how and what the government’s role in that should be.