Commons speaker John Bercow told MPs the Queen had given Royal Assent to what is now the Wales Act 2017.
The legislation devolves to Wales extra powers over transport, energy, electoral arrangements and an element of control over income tax levels.
It also defines what is under the control of Westminster, with everything else assumed to rest with the assembly - known as the "reserved powers" model.
The current system specifies what is under assembly control, with everything else assumed to lie with Westminster.
The UK government has said the new law "brings clarity to the settlement and accountability for Welsh Government".
But critics, including Welsh ministers, have complained that it imposes too many restrictions.
Earlier in January, First Minister Carwyn Jones said the legislation could be better but it "takes Wales forward".
The date when many of the act's provisions, including the reserved powers system, has not yet been decided.
Welsh Secretary Alun Cairns will consult the Welsh Government and the assembly's Presiding Officer, Elin Jones, on the timescale.
The Wales Bill, rewriting the devolution settlement, has become law.