War with Spain was not on the ballot paper when Britons went to the polls in last year’s referendum and voted to withdraw from the European Union.

But Prime Minister Theresa May was forced to rule out the prospect of military action to defend the British enclave of Gibraltar on Monday, after a former leader of her Conservative Party seemed to suggest that might be necessary to keep Spain from demanding the territory’s return as part of the deal to allow the United Kingdom to trade freely with remaining E.U. members.

Speaking on Sunday, Michael Howard, who is now a member of the House of Lords, suggested that if Spain tried to assert sovereignty over the outpost, the British prime minister could emulate her predecessor, Margaret Thatcher, who used force to keep control of another Spanish-speaking nation, Argentina, from seizing another British enclave, the Falklands.