http://www.whitehouse.gov/briefing-room/presidential-actions/executive-orders
In his speech to the nation, he spoke of 23 "executive actions"...
These are a few of the 23 executive actions that Im announcing today. But as important as these steps are, they are in no way a substitute for action from members of Congress. To make a real and lasting difference, Congress, too, must act -- and Congress must act soon. And Im calling on Congress to pass some very specific proposals right away.
http://www.whitehouse.gov/the-press-office/2013/01/16/remarks-president-and-vice-president-gun-violence
He did however, issue 3 Presidential Memoranda on the issue...
http://www.whitehouse.gov/the-press-office/2013/01/16/presidential-memorandum-engaging-public-health-research-causes-and-pre-0
http://www.whitehouse.gov/the-press-office/2013/01/16/presidential-memorandum-improving-availability-relevant-executive-branch
http://www.whitehouse.gov/the-press-office/2013/01/16/presidential-memorandum-tracing-firearms-connection-criminal-investigati
The difference between the two (executive order, presidential memoranda), is a subtle one, issued for the purpose of being less controversial and easier to swallow.
Another executive tool which has raised many questions is the presidential memoranda. Although they possess a different title than executive orders, it appears as though these instruments are very much alike. Both are undefined, written instruments by which the president directs, and governs actions by, Government officials and agencies. They differ in that executive orders must be published in the Federal Register whereas presidential memoranda are similarly published only if the President determines that they have a "general applicability and legal effect." .... In at least one instance, a federal district court seemed to use the two terms interchangeably.
Basically, for all intents and purposes, a memorandum is an executive order. However, since executive orders are a particularly controversial and politically charged lever of presidential power (the mere mention of them has inspired talk of impeachment among some of Congress's more firebrand Republicans), it's important to note that they (or something exactly like them) comprised only three of the items on Obama's list of 23 "executive actions."
http://nymag.com/daily/intelligencer/2013/01/obama-23-executive-orders-actions-gun-control.html
So, are these 3 "Presidential Memoranda" unconstitional?
IMHO, no (disclaimer, I'm neither a Constitutional scholar or lawyer, and for that matter neither am I a Western sheriff or talk show Reverend).
They're simply instructions/orders to the relevant agencies of the Executive branch to carry out new guidelines.