Well, yes, a company is bound by it's employees' representations.
If it was cash or merchandize, they would be legally required to make good on their promise (and may take action against the employee).

But since it's points, and just like any frequent guest /flyer program, the terms of use give them great latitude as to what they can do, no you do not have a legal standing on that one.

You agreed to this https://www.starwoodhotels.com/prefe...spg_terms.html when you signed up:

"1.11 All interpretations of these Terms and Conditions, and the rules of Membership, shall be at our sole discretion, and our decisions shall be final. We may waive compliance with these Terms and Conditions in our sole discretion and we may run promotions from time to time that provide enhanced benefits to select Members. Notwithstanding the foregoing, our failure to exercise any of our rights under this Agreement or our delay in enforcing or exercising any of our rights shall constitute a waiver of such rights. If we waive any right on one occasion, such waiver shall not operate as a waiver as to any other occasion.

3.5. We may cancel accumulated Starpoints, suspend your Membership privileges or terminate your Membership at any time with immediate effect, confirmed by written notification to you if, in our sole discretion, you have (a) acted in a manner inconsistent with applicable laws or ordinances, (b) acted in a fraudulent or abusive manner, (c) breached any of these Terms and Conditions, (d) engaged in fraud or abuse concerning Starpoints, award usage or Membership privileges and benefits, or (e) failed to pay any bill when due to Starwood Hotels or any Participating Property. Subject to applicable law, Membership will terminate automatically on your filing for bankruptcy or otherwise becoming subject to a bankruptcy proceeding.

5.12. We reserve the right to deduct any Starpoints credited to a Membership account in error without notice. If refunds are made to you in respect of goods or services for which you received Starpoints, Starwood Hotels will adjust the number of Starpoints awarded."

As per 1.11, they may just not give you the points at their sole discretion.
Or, they could give you the points and take them away the very next second, as per 3.5 or 5.12

Besides "1.3 Starpoints and your Membership are not your property and belong to us"