这里，absent 不是形容词（缺席的；不在场的），而是介词。意为“如果没有”。意思上相当于without，表示“条件”。属于美国英语比较正式的文体。

以下为《柯林斯词典》的解释：

PREP 若没有；假设没有

If you say that absent one thing, another thing will happen, you mean that if the first thing does not happen, the second thing will happen.

Absent a solution, people like Sue Godfrey will just keep on fighting. 

假如得不到解决，像休·戈弗雷这样的人就会一直坚持斗争下去。

网友的句子：

As previously noted, newly amended provisions in the new Foreign Investment Law prohibiting forced technology transfer are likely to have little impact absent effective complaint and legal challenge procedures, such as the creation of a foreign investment ombudsman and/or appeals to the newly established IP court. 

如前所述，新《外国投资法》中禁止强制技术转让的新修订条款，如果没有有效的投诉和法律挑战程序，如设立外国投资监察员和/或向新设立的知识产权法院提出上诉，可能不会产生什么影响。

又如：

Absent this kind of early instruction, absent the building of this moral shield, no congressional law, no presidential executive order, no fiery rhetoric will salvage a child' s conduct nor locate a missing moral care.

假如没有这种早期的指导，假如没有这种道德盾牌的建立，那么，任何国会法律，任何总统的行政命令，任何激烈的言辞，都不会挽救一个孩子的行为，也不会找到缺失的道德关怀。

in the absence of：这是个短语介词。意为“在没有...情况下；在缺少...时”。

Although these changes are positive, I am reluctant to enthusiastically endorse them in the absence of corresponding measures ensuring their implementation.

虽然这些变化是积极的，但在没有确保其执行的相应措施的情况下，我不愿热情地支持这些变化。