A US legislator who authored a law that keeps most of the state of Arkansas' lethal injection policy a secret has challenged the right of pharmaceutical producers to object to prisons using their drugs in executions. Earlier this week, the news agency Associated Press (AP) said it appeared that Arkansas had obtained a paralytic drug, vecuronium bromide, made by a subsidiary of Pfizer for use in the death chamber, even though the largest US drugmaker has restricted its use to exclude executions.

AP quoted State Representative Doug House, a Republican, as saying that while Pfizer may complain about the possible unauthorized use of one of its products, no drugmaker can file complaints with the state Department of Correction.

Referring to the Pfizer product, which is included in a three-drug “cocktail” authorized for use by Arkansas prison – the state has not executed an inmate since 2005 because of legal challenges and the difficulty of obtaining execution drugs – House reportedly said the state “bought it legally, fair and square,” adding that, if Pfizer doesn’t want its drugs used in this way, it will have to put pressure on its distributors.

A number of the 31 US states that have the death penalty have passed laws allowing them to withhold information about which drugs they use in lethal injections, in some cases shielding companies willing to sell products for execution but afraid of negative publicity.

The secrecy laws stem largely from a controversy over the sedative midazolam, which has been linked to at least two highly publicized botched executions. The substance has been widely criticized, and some states have tried to avoid using it, even though the US Supreme Court last year, in a 5-to-4 vote, upheld its use.

Pfizer manufactures seven drugs that could be used in lethal injections and has limited their sale to a small group of wholesalers, distributors and direct purchasers. In April of this year, the company updated its guidelines to guarantee that the products do not fall into the hands of prisons carrying out the death penalty. In announcing the changes, Pfizer said it would “consistently monitor” distribution.

The EU imposed an export ban on drugs for lethal injection in 2011. With more and more drugmakers restricting or banning their drugs from use in executions, US prisons have increasingly turned to “gray market” sources, often unlicensed manufacturers in the UK or India, or contracting with local drug compounders. In many cases, the US Drug Enforcement Agency (DEA) and the Food and Drug Administration (FDA) have seized the states’ illegal supplies.

A Pfizer spokesperson said the company is “communicating with states to remind them its products are intended to save lives, not end them.”