The alliance believes the move runs a high risk of European consumers eating tainted imported horse meat.
It accuses the American government of abetting the process. "In 2008, 134,059 American horses were sent to Canada and Mexico for slaughter for consumption in the European Union with no regard as to the drugs they had received," it said.
In Europe, horse passports record the drugs a horse has received from birth and, because of those drugs, many are disqualified from entering the food chain.
The alliance points out that Canada and the United States do not regulate nor track this information in horses.
The EU is now insisting that countries supplying horse meat follow guidelines it issued in April, but the alliance says it is apparently relying on the US and Canada for enforcement of an affidavit system.
In August 25, the alliance and the Canadian Horse Defence Coalition issued a press release questioning the Canadian Food Inspection Agency on how the European guidelines issued in April would be enforced.
The guidelines, issued to "third" countries, outlined requirements for equines intended for food production, including a system of identity verification, a prohibition on banned substances and a minimum six-month withdrawal period for drugs commonly used by American horsemen.
The alliance says it has now learned the EU will accept affidavits from kill buyers and haulers employed by the offshore slaughter industry as proof that animals have passed the quarantine period.
"It is inconceivable that the EU is prepared to trust the word of kill buyers and haulers, many with criminal records, to protect the health of European consumers," the alliance said in a statement.
"Currently, there is no mechanism in place to keep these profiteers honest."
The alliance says the "overwhelming majority" of North American horses have received toxic wormers, drugs such as phenylbutazone (bute) and even fertility drugs that can cause miscarriages in women - all banned substances in animals intended for food.
Phenylbutazone is a known carcinogen and can cause aplastic anaemia (bone marrow suppression).
Alliance spokeswoman Vicki Tobin said: "If these animals were livestock, the US Department of Agriculture would never allow them to enter the food chain in the United States. I don't understand how our government is allowing Europeans to consume horse meat with banned substances."
The Canadian Horse Defence Coalition's Sinikka Crosland said: "Drug-free equine meat from these horses is not an attainable goal, and without any enforcement mechanism the proposed system will be totally ineffective."