Stealing from anyone is a risky exercise, but stealing from someone who has both the ability and the motivation to punish you - such as the inhabitants of the military camp on the Seven of Swords - is often downright foolish. Such cunning and confidence are two of the hallmarks of the Seven of Swords, as it stands for those times when guile and diplomacy will bring about the results that brute force will not. But the Seven of Swords has that same double edge as the rest of the cards in its suit, and thus it implies that you can be the victim of such deception.
Whether or not the outcome is successful, the Seven of Swords usually refers to plans in which deception or guile is a key factor. This is the card of the con artist, the thief and the trickster. All of these types of people usually work alone, fearing that the incompetence of others will interfere with their work. Hence they develop a kind of "Lone Wolf" mentality which could eventually prove detrimental. On the Rider-Waite card, the man cannot carry all of the swords and must leave two of them behind. By implication, this is an incomplete victory, though success appears to have been achieved.
At other times the victory is not so complete. The Seven of Swords often shows or predicts a loss due to cunning and trickery. The cunning may be that of another person who cheats you out of a hard-earned victory, or who swindles your money away from you. Or it could be your own trickery that leads to your undoing. Both of these scenarios offer lessons. The unethical victory of another person should be used as a model of what to watch for in similar situations in the future. On the other hand, having your deception exposed should teach you that deception is not the best way to win!
The last meaning of the Seven of Swords, one that is not too apparently connected with the others, is indecision. When you have to do what you felt was wrong in order to succeed, or when you do something that you thought was right but that put you in danger, your whole ethical system can be challenged and warped. If you have to compromise your values in order to achieve the goals you have set, you should either revise your ethics or re-evaluate your goals - probably the latter. Society as a whole does not look well upon the Machiavellian belief of ends justifying means. The vigilante approach of the Seven of Swords is rarely the best one.