No and hell no. In any system -- at any time.
Lawful Good is not a synonym for stupid; nor is honourable another way of saying "suicidal".
In all honesty, I find these kind of questions quite aggravating, because so often they betray a tendency among some groups to enforce this sort of nutty code of conduct when discussing Paladins. There simply is no justification for this in any code of honour or alignment, for any version of the game, at any time, over the past 36 years the Paladin class has been in the game (since OD&D - Greyhawk).
No wonder the Paladin gets a bum wrap so often.
Lest ANYONE take offense at the above post, I believe this person,...did not read 1eUA page 16 and allow for differences of play. (Edit:1eUA is another edition of D&D, notably under AD&D...different rules and different ideas. This is where the idea of Paladin's, who were considered Cavaliers...must engage enemies on sight. There was even an order to what they would have to engage. This was a balancing factor due to some of the bonuses that Cavaliers and Paladin's recieved...such as an additional percentage to their STR, DEX, CON, every level...till they hit 18's, etc..., I would not be so stringent in my interpretation of the rules in THAT edition, but if a DM was clear about that interpretation, I wouldn't have a problem with that interpretation IN THAT EDITION. This IS and WAS NOT 3e...just to be clear. This is merely where some of the ideas came from.)
While I agree Lawful Good is not Lawful Stupid (or as per page 16 in UA, Lawful doesn't necessarily mean lawful stupid, the rule that a Cavalier [or which the paladin is a subclass in UA rules] MUST CHARGE an enemy can also be seen as a weakening of what some may call an overpowered class).
Many would play Cavaliers, or Paladin's who were under the Cavalier rules, and blatantly ignore rules. It was more a roleplaying item to balance out mechanical rules.
UA page 16 is a different playstyle and a different edition than 3e or Pathfinder...but holdouts may still adhere to these rules which is where such confusion for the original poster came from. In those editions as long as the DM was clear on how he/she interpreted such Codes of Conduct from a Cavalier or Paladin, I find it completely acceptable.
Such codes ARE NOT FOUND in 3e or Pathfinder to my knowledge.
The reason the Paladin get's a bum wrap under the new editons with their code of conduct has more to do with them attacking party members and evil on sight as per the original 3e rules under Paladin Code of Conduct regarding associates which reads
"A paladin will never knowlingly associate with evil characters. A paladin will not continue an association with someone who consistently offends her moral code. A paladin may only hire henchmen or accept followers who are lawful good."
Which has probably resulted in more than a few clashes within a party and the deaths inherent to such a clash.
I personally probably allow more leeway (both in the 1eUA case and the 3e case)...unless the person is an absolute rules lawyer in which case I'd enforce the rules...BUT...in either of the cases 1e or 3e...I'm not going to butt in and say it's not acceptable to play by those rules.
Also, as stated earlier, 3e is NOT AD&D or D&D from the older editions, it has other rules and there is no reason to follow the rules of an older edition. If a DM is doing so they should make it abudantly clear.
In regards to 3e, and Paladin's sneaking off I agree with what has already been stated in this thread, and that there should be no penalty for such. In fact perhaps such a move should be rewarded even.
I wouldn't think enforcing a 3e mindset on another version of the game is apt however...anymore than enforcing a UA rules mindset on 3e without player consent is apt.
Just my two cents, and trying to be polite and not offensive in my reply.