JSFiddle - React, Tailwind, and code Playground

HTML

<p>
  Some custom wording goes here
</p>
<p>
  <label>
    <input type="checkbox" id="checkbox">
    GDPR Checkbox
  </label>
</p>
<p>
  <button id="submit" type="submit" disabled>Submit</button>
</p>

JavaScript

var checkbox = document.getElementById('checkbox');

function allowRegister(checkbox, submit) {
  var submit = document.getElementById('submit');
	if (checkbox.checked) {
  	submit.disabled = false;
  }
  else {
  	submit.disabled = true;
  }
}

// Initial check just incase the page gets refreshed and the form is saved
allowRegister(checkbox);

// Also execute the function when checking the checkbox
checkbox.addEventListener('change', function(){
	allowRegister(this);
});