France, controlled by a Popular Front government, had a policy of 'relaxed non-intervention'. Therefore, they aided without breaching the treaty:
sent non-military aid - food, medicine
allowed Soviet troops to use French land to receive supplies
allowed French communist party to organise voluntary aid
gave credit to buy foreign supplies
In 1937, Britain established naval patrols to stop supplies for Franco reaching Spain. In September 1937, they also negotiated a deal with Italy to halt Italian submarine attacks on the Republican navy.
It was discovered in the USA, by 1937, public opinion supported the Republicans. Therefore, the US communist party sent small quantities of aid to the Republic.
However, on the whole, governments adopted policies that best served their national interest.