Experience letter and relieving letter

I had left A company(previous) for almost a year they didn't issue me a experience letter but instead gave a relieving letter, then starting working with another company(current) here i didn't face issues with the background verification since i forwarded them the relieving letter of previous company, now i have applied for a new company(prospective) and they required a experience letter or Service letter to reflect my employment tenure with the A company previous, Acompany previous had only issued me a relieving letter with the last date of employment on it. I have written mails after one year to them to either revise by relieving letter mentioning on it the Joining date and last working date or the experience letter. But they refuse to give experience letter or revise the relieving letter stating that it is as per their policies of the company not to issue experience letter to employees who leave the company within one year. Can Companies frame such policies ? whether such policies supersede labor laws? Does any laws restrict from having date of joining on the relieving letter?