The three laws cited include the 2004 act introducing the new contract into Scotland - making any change a further blow to the UK-wide contract.
In an open letter, GPs, academics and socialist politicians welcomed health minister Nicola Sturgeon's guarantee that there would be 'no privatisation' of any GP services in Scotland.
But they warned that the guarantee could be undermined by current laws, which open all tenders to provide GP services to any provider.
The letter argues that allowing commercial providers to supply primary care 'will be destructive for patients and costly for government. However, in Scotland, legislation is still in place that enables ... for-profit commercial providers (to) compete for patients and money'.
Dr Chris Johnstone, a GP in Paisley and one of the letter's signatories, said that the market for GP services had been opened up as a direct result of the 2004 contract.
'Part of the deal was that we'd lose the monopoly over general medical services that we've had since 1948,' he said.
He said that doctors wanted to see Ms Sturgeon 'put her money where her mouth is' by changing the laws around the contract, to ensure that future executives cannot reverse her anti-privatisation policies.
No private providers have yet signed up to provide GP services in Scotland. An unsuccessful bid by Serco to run a GP surgery in Harthill, Lanarkshire, resulted in public protests and questions in parliament.
However, campaigners fear that, unless the law is changed, other companies will either win future tenders, or successfully challenge their failure under EU competition laws.