People stand next to a closed gate while a Venezuelan soldier stands guard at La Union international bridge, on the border with Colombia, on Aug. 29. (Carlos Eduardo Ramirez/Reuters)

WITH INFLATION and violent crime soaring and supplies of food and medicine shrinking, Venezuela’s populist government appears headed toward a major defeat in legislative elections scheduled for December, if the vote is free and fair. So it’s no surprise that President Nicolás Maduro is resorting to the assaults on the opposition and manipulations of the electoral system that have been a staple of the regime created by the late Hugo Chávez. A number of opposition leaders have been banned from participating in the election, districts have been redrawn and the government-controlled supreme court replaced the leaders of one opposition party with its own nominees.

Now Mr. Maduro has resorted to provoking a crisis with Venezuela’s neighbor, Colombia. On Aug. 21 he declared a state of emergency along parts of the border, claiming that an attack on a Venezuelan patrol had been carried out by Colombian paramilitaries at the instigation of former president Álvaro Uribe. This ludicrous charge provided the pretext for a crackdown that has seen Venezuelan soldiers expel some 1,000 Colombian migrants across the border and demolish homes in a frontier city. Another 9,000 Colombians are reported to have fled Venezuela, creating a humanitarian emergency. As these poor and desperate people have tried to rescue their homes and possessions, Mr. Maduro has staged rallies in far-away Caracas to trumpet what he calls “a plan of liberation and sovereignty on our border.”

In reality, lawlessness and smuggling are rife along the Venezuelan-Colombian border — but the trouble has been caused not by Colombians but by the Maduro government’s disastrous economic policies. The state virtually gives gasoline away, charging a fraction of a cent per gallon in the devalued national currency, while in Colombia prices are at world market levels. So thousands of gallons of gas, along with other subsidized goods, flow across the border daily. However, the most trafficked smuggling routes are not in the region where Mr. Maduro launched his crackdown but further south — and the flow is controlled not by poor migrants but by corrupt Venezuelan army officers.

Sadly, the Organization of American States has proved unable to address this outrage: Venezuela’s allies, including Caribbean countries it has supplied with discounted oil, on Monday blocked a motion to convene a foreign ministers’ meeting on the expulsions. The Obama administration, which has recently pursued a diplomatic dialogue with the Maduro government, has limited itself to a tepid expression of “concern” about the “worsening humanitarian situation.”

Fortunately, the democratic Colombian government of Juan Manuel Santos, recognizing Mr. Maduro’s action for the cynical provocation that it is, has reacted with restraint while seeking to aid the migrants. But those who have been expelled are unlikely to be the last victims of a regime unable to arrest an accelerating economic and social descent. This Friday, the trial of opposition leader Leopoldo López is expected to conclude; government prosecutors have proposed a sentence of up to 13 years on blatantly trumped-up charges. The United States’ and Latin America’s democratic governments should be warning the Maduro regime now that a conviction will harm relations and will prompt a meaningful response — including sanctions against all those officials involved in the trial.