From the Steam Subscriber Agreement:
3. BILLING, PAYMENT AND OTHER SUBSCRIPTIONS
A. Payment Authorization
You agree that you will not use IP proxying or other methods to disguise the place of your residence, whether to circumvent geographical restrictions on game content, to purchase at pricing not applicable to your geography, or for any other purpose. If you do this, Valve may terminate your access to your Account.
Emphasis mine. I would highly recommend not spoofing or using proxies to disguise your IP in order to circumvent blocks (on game activation or play). Doing so will run the risk of having your account suspended or terminated.
Further to this: by default, Steam will always try to show you the Storefront from your 'home' region, even when traveling:
What if I am traveling and the product I am trying to purchase has a note about region restrictions?
If you are currently traveling, please ensure that your store region is correctly set to the country where you permanently reside as shown below. You may view and change your store region from your Account Details page. Learn how to change your store country.
And Steam clearly labels any Steam Gifts as being region locked:
Are Steam gifts region restricted?
Gifts purchased in certain regions can be redeemed only in those regions. When you purchase a gift you will be notified at checkout of any restrictions that will be placed on the gift. An example of a gift purchase in Russia and the countries that the gift can be redeemed in is shown below:
I received a Steam gift. How will I know if it has a region restriction?
Each gift will clearly note in the gift's description which countries it can be redeemed in. You can view the description from your Steam gift inventory.
Steam Support cannot modify region restricted gifts. You should contact the friend who gave you the gift to return it or have them ask for a refund.
You can read more about Steam's Region Restrictions on their Support Page