$obIBlock = new CIBlock;
$arIBlockFields=$obIBlock->GetFields($arIBlock["ID"]);
$arIBlockFields["IBLOCK_SECTION"]["IS_REQUIRED"]="Y";
$arIBlockFields["CODE"]["IS_REQUIRED"]="Y";
$arIBlockFields["CODE"]["DEFAULT_VALUE"]["UNIQUE"]="Y";
$arIBlockFields["CODE"]["DEFAULT_VALUE"]["TRANSLITERATION"]="Y";
$arIBlockFields["TAGS"]["IS_REQUIRED"]="Y";
$obIBlock->SetFields($arIBlock["ID"],$arIBlockFields);