Was being in the European union a form of treason?

Yup lots of treasonous acts have been perpetrated over the last 40 years by politicians in both mainstream parties. The 2-party political system is of course a complete sham. No matter whether you voted Tory or Labour, you were inadvertently voting for unseen, unelected EU masters who, using those puppets moved the UK into the EU bit by bit through stealth and skulduggery.

In doing so, they wilfully trampled on the "British Constitution" which comprises law and acts that have been in place for 100s of years like the Magna Carta and Bill Of Rights.

It absolutely IS TREASON to sell the sovereignty of a country and its justice system to a foreign power and thus every politician who had a hand in this HAS committed treason and should be put on trial for the same.
Sadly this also includes HM The Queen who has given Royal Assent to each of those fraudulent EU treaties.

It was treason, Edward Heath was told about it being treason by letter, which has recently been in the papers. This is what was in said letter.
Edward Heath's government deceive the British people when he held back the information within the letter. He went on to sign us into the EEC
However It was John Major who finished the job off with the maastricht treaty in 1991.

Maybe lay off drinking the Toilet Duck for a few days, lads.

Mock all you like, it's researched law. Theresa May is also liable for fraud charges. fraud act 2006
https://www.legislation.gov.uk/ukpga/2006/35