Intra Vires

'Intra vires' is defined by contrast with its far more commonly used opposite, 'ultra vires'. Official Cabinet Office guidance for government decision-makers, 'The Judge Over Your Shoulder', explains that the term ultra vires literally means 'beyond the powers' in Latin — for example, if a decision maker acts outside their power for a purpose that the power was not created to achieve, that action (often in the form of a decision) will be ultra vires. An intra vires act is simply one that stays within that lawful scope, and so is immune from challenge on the ground of illegality in judicial review.

The distinction also has practical bite in company and tax law. HMRC's own internal manual on ultra vires dividends explains that where a company declares a dividend but there were insufficient distributable reserves to cover the dividend, so the dividend was 'ultra vires', or unlawful — meaning it fell outside the company's legal power to distribute in the first place, with consequences for both the shareholders who received it and the company's tax position.

In public law, whether a body has acted intra or ultra vires is one of the core grounds of judicial review (traditionally labelled 'illegality'), alongside irrationality and procedural impropriety, and is the starting point for assessing whether a public body's decision or subordinate legislation is lawful.