BRUSSELS (Reuters) - British Prime Minister Theresa May said on Friday  people should be abiding by the rule of law and uphold the Spanish constitution , clearly siding with Prime Minister Mariano Rajoy in the central government s standoff with Catalonia.  I have spoken to Mariano Rajoy this morning as I did earlier this week and made clear that the United Kingdom s position is very clear,  May told reporters after two days of talks between EU leaders in Brussels.   We believe that people should be abiding by the rule of law and uphold the Spanish constitution,  May said in Brussels, were EU leaders showed little political support for Catalonia.  