How to make checkbox mandatory even on bowser back button click using jquery?

I am facing a situation like below.

1. WebPage1 with fields and a check box (Agree terms)
2. WebPage2 check if checkbox is checked and initiates emailing

After the page1 form fields are filled, checkbox is checked (I agree to terms) and submitted to Page2, Page2 detects checkbox checked state and proceeds emailing. - works fine

Now the issue is, if in the browser "Go back button" is clicked while in page2, page 1 gets loaded (checkbox shows unchecked) and then if browser "Go forward button" is pressed WITHOUT checking the checkbox, page1 gets submitted and page2 starts emailing.

I want the checkbox to be mandatorily checked before going to Page2 even if the browser Back and Forward buttons are used by the user.

How can this be achieved ? Please help.